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Paradox unexplained



 
 
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  #1  
Old April 1st 16, 03:47 PM posted to sci.astro.research
Jos Bergervoet
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Posts: 126
Default Paradox unexplained

For the black hole information paradox I would expect
two seemingly conflicting results (as is necessary for
a paradox by definition,) e.g. like:

1) We know that information is lost because [...]
2) But also that it is not lost because [...]

Unfortunately I cannot find it clearly explained in
that way. To be honest, I cannot even find the first
statement clearly explained.

What I mean is: by using Kruskal-Szekeres coordinates
we can follow any molecule, or larger object, that
enters the black hole, and there is no clear indication
that it ever loses information at all! There might be
tidal forces tearing it apart, but that need not in
general destroy information and also that need not
happen at the event horizon (in fact the Schwarzschild
radius has no special local properties at all, as the
K-S coordinates prove). Finally, singularities may be
present somewhere inside, but we don't know the physics
there, so we cannot claim anything about what happens
to information at those sites.

Actually, for statement 2) I also never found a really
satisfying explanation, but let's leave that out, since
without *two conflicting statements* there is no
paradox anyway.

So why do people feel there is a paradox?!

--
Jos
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  #2  
Old April 2nd 16, 08:25 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default Paradox unexplained

On Friday, April 1, 2016 at 10:49:07 AM UTC-4, Jos Bergervoet wrote:

So why do people feel there is a paradox?!


You are correct in implying that this paradox cannot be satisfactorily
answered using theoretical models - far too much uncertainty in any
"conclusion".

The first assumption: that information is lost, for many people, comes
from variations on the following thought experiment. Throw an
encyclopedia into a black hole. What is the probability that one could
recover all the information exactly. Answer: either 0 or effectively
0.
  #3  
Old April 3rd 16, 09:15 AM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Paradox unexplained

Op vrijdag 1 april 2016 16:49:07 UTC+2 schreef Jos Bergervoet:
For the black hole information paradox I would expect
two seemingly conflicting results (as is necessary for
a paradox by definition,) e.g. like:

1) We know that information is lost because [...]
2) But also that it is not lost because [...]

Unfortunately I cannot find it clearly explained in
that way. To be honest, I cannot even find the first
statement clearly explained.

Actually, for statement 2) I also never found a really
satisfying explanation, but let's leave that out, since
without *two conflicting statements* there is no
paradox anyway.

So why do people feel there is a paradox?!


I understand your frustration.
In a sense when there is an information issue for a BH
than there should also be an information issue for the Sun.
when you drive in a car our brain (via our eyes) continuously receives
and creates new information and old information is erased and lost.
From a physical point, in order to understand the universe, this
information transfer process in our brain is completely unimportant.

When a comet collides with the Sun, before that event, we are capable,
based on a limited set of observations, to calculate the past
and future of that comet outside that range. After the collision we
know that the mass of the Sun has increased slightly and that
the trajectory of the Sun was affected. But if we want to calculate
the past of the Sun based on a limited set of observations
(after this collision event) we can not do that accurately.

The same problem exist for a BH. This has nothing to do that we humans
cannot observe a BH. After a collision of a star with a BH the two melt
together into one larger object and the physical details of each
before the event are physical lost. That is the physical reality.
In all these three cases I "see" no paradox.

Nicolaas Vroom
http://users.telenet.be/nicvroom/wik...on_paradox.htm
  #4  
Old April 3rd 16, 10:32 PM posted to sci.astro.research
Steven Carlip
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Posts: 9
Default Paradox unexplained

On 4/1/16 4:47 PM, Jos Bergervoet wrote:
For the black hole information paradox I would expect
two seemingly conflicting results (as is necessary for
a paradox by definition,) e.g. like:

1) We know that information is lost because [...]


We believe that matter in a pure quantum state can collapse
to form a black hole. Such a black hole will then evaporate
by Hawking radiation, which is thermal. When the black hole
has completely evaporated, the net result will be the conversion
of a pure state to a mixed state. This is what is meant by
"information loss" -- quantum mechanically, a pure state contains
the maximum information about a system, while a thermal state
contains the minimum amount of information.

2) But also that it is not lost because [...]


Quantum mechanics is unitary. This means that the "fine-grained"
information in a quantum state is never lost; pure states evolve
to pure states. (Think of this as a quantum version of time
reversal invariance -- if you are given a final state, you can
in principle evolve it back to the initial state.)

There are some obvious places to look for loopholes. I suspect
that at least the obvious ones have all been analyzed to death,
and all have unpleasant consequences. For instance, Hawking
radiation might not really be thermal; but to get back enough
correlations seems to require some very nonlocal interactions.

[...]
What I mean is: by using Kruskal-Szekeres coordinates
we can follow any molecule, or larger object, that
enters the black hole, and there is no clear indication
that it ever loses information at all! There might be
tidal forces tearing it apart, but that need not in
general destroy information and also that need not
happen at the event horizon (in fact the Schwarzschild
radius has no special local properties at all, as the
K-S coordinates prove). Finally, singularities may be
present somewhere inside, but we don't know the physics
there, so we cannot claim anything about what happens
to information at those sites.


That's absolutely correct classically. The problem only
appears quantum mechanically, when you allow black holes
to evaporate thermally via Hawking radiation.

Steve Carlip
  #5  
Old April 7th 16, 12:13 PM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Paradox unexplained

Op zondag 3 april 2016 23:33:21 UTC+2 schreef Steven Carlip:

We believe that matter in a pure quantum state can collapse
to form a black hole.

This is in a certain sense equivalent that a star collapses and becomes
a neutron star
Such a black hole will then evaporate
by Hawking radiation, which is thermal.

This is in a certain sense equivalent that a star explodes and
becomes a super novae.
The issue is if in either of these cases you can speak about
information loss?
To answer the questions you must have a clear definition of what
information means and what a pure and mixed quantum states are.
To start with the second, my interpretation of a pure quantum state
is that an object as such is completely everywhere physical
and chemical identical. They have no structure.
The four important parmeters a Radius, Volume, Mass and density.
In a pure quantum state object the density is everywhere the same.
My interpretation of a mixed state is that it has a structure.
For example in the Sun and in planets when you "travel" towards
the center the density changes.

When the density and chemical composition inside a BH is everywhere
the same than the information content is zero compared to the encyclopedia
britanica. The text of a book contains knowledge and information.
Along that line when you burn a book it is information loss.

IMO it is much more important to understand the intial conditions and
the whole life cycle process of a Black Hole until his dead.
I doubt if the concept of information is in anyway important in order
to understand this physical process.

When the black hole has completely evaporated,


The issue is here how do we know that BH physical can evaporate and
change into a gaseous (visible?) state.

The problem only
appears quantum mechanically, when you allow black holes
to evaporate thermally via Hawking radiation.


The problem is much more a physical, chemical problem.
At the same time it is also an information problem in the sense that
we cannot directly observe a BH. That means it is extremely difficult
to observe that the life cycle time of a BH is finite.
It is a murder without a body. For a star this is much simpler.

Nicolaas Vroom
  #6  
Old April 8th 16, 08:59 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default Paradox unexplained

In article , Nicolaas Vroom
writes:

We believe that matter in a pure quantum state can collapse
to form a black hole.


This is in a certain sense equivalent that a star collapses and becomes
a neutron star

Such a black hole will then evaporate
by Hawking radiation, which is thermal.


This is in a certain sense equivalent that a star explodes and
becomes a super novae.
The issue is if in either of these cases you can speak about
information loss?


Especially with respect to information loss, the two cases are not
equivalent in any meaningful sense. The whole information-loss problem
stems from the fact that, at least classically, a black hole has no
hair, meaning it is COMPLETELY characterized by charge, mass, and
angular momentum. This is not the case for a neutron star.
  #7  
Old April 8th 16, 09:00 AM posted to sci.astro.research
Steven Carlip
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Posts: 9
Default Paradox unexplained

On 4/7/16 4:13 AM, Nicolaas Vroom wrote:
Op zondag 3 april 2016 23:33:21 UTC+2 schreef Steven Carlip:


We believe that matter in a pure quantum state can collapse
to form a black hole.


This is in a certain sense equivalent that a star collapses and becomes
a neutron star


Not really. A collapsing star is very unlikely to be in a pure
quantum state.

Such a black hole will then evaporate
by Hawking radiation, which is thermal.


This is in a certain sense equivalent that a star explodes and
becomes a super novae.


No. Here things are very different, because a black hole has an
event horizon.

Think of the first photon coming out of a supernova. That photon
will be correlated with the remaining bits of the star, which, in
turn, affect the next photon coming out. This allows the second
photon to be correlated with the first. Similarly, the second
photon is correlated with the remaining bits of the star, so the
third photon can be correlated with the first two. If the supernova
explosion destroys the star completely, the photons that come out
can still be highly correlated.

A black hole is different. The first photon of Hawking radiation
will be correlated with something, but the thing it's correlated
with is behind the horizon. That means that it *can't* transfer
the correlation to the next photon, at least not by any local
physical process. So unlike the case of the supernova, there's
no easy way for the Hawking radiation photons to be correlated
with each other. That means that the correlations in the initial
state that formed the black hole get lost.

The issue is if in either of these cases you can speak about
information loss?


In the first case, there's "coarse grained" information loss --
it's *hard* to recreate the state of the star by looking at the
correlations among the photons that come out. But it's not
impossible. In the second case, the conventional picture of
Hawking radiation implies that there is no correlation among
the photons, so the information is genuinely completely lost.

To answer the questions you must have a clear definition of what
information means and what a pure and mixed quantum states are.


Yes, but this is standard quantum mechanics. You can make up
your own definitions, but then you'll no longer be talking about
the same problem.

To start with the second, my interpretation of a pure quantum state
is that an object as such is completely everywhere physical
and chemical identical. They have no structure.
The four important parmeters a Radius, Volume, Mass and density.
In a pure quantum state object the density is everywhere the same.


This is not what the term means.

My interpretation of a mixed state is that it has a structure.
For example in the Sun and in planets when you "travel" towards
the center the density changes.


This is also not what the term means. There's a nice explanation
in the Wikipedia page under "Density matrix." If you want to
talk about the black hole information paradox, you need to use
the correct definitions.

When the density and chemical composition inside a BH is everywhere
the same than the information content is zero compared to the encyclopedia
britanica. The text of a book contains knowledge and information.
Along that line when you burn a book it is information loss.


That's not what "information" means in this context. In the black
hole information loss problem, the term "information" has a very
specific, technical meaning -- it's described by the von Neumann
entropy of the density matrix.

[...]
When the black hole has completely evaporated,


The issue is here how do we know that BH physical can evaporate and
change into a gaseous (visible?) state.


"Evaporation" here has nothing to do with "gaseous" -- it just means
that the mass of black hole is converted completely to Hawking
radiation.

How do we know this happens? By doing a computation in quantum
field theory to predict the evolution of a black hole. Now, the
answer to the paradox may be that we're doing the computation
wrong, but that's not a real answer unless you can say exactly
*where* the computation is going bad.

The problem only
appears quantum mechanically, when you allow black holes
to evaporate thermally via Hawking radiation.


The problem is much more a physical, chemical problem.


No, it's not. You are free to invent a different problem, but
that's not the one that's called the black hole information
paradox.

Steve Carlip
  #8  
Old April 8th 16, 10:20 PM posted to sci.astro.research
jacobnavia
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Posts: 105
Default Paradox unexplained

Le 01/04/2016 16:47, Jos Bergervoet a écrit :
For the black hole information paradox I would expect
two seemingly conflicting results (as is necessary for
a paradox by definition,) e.g. like:

1) We know that information is lost because [...]
2) But also that it is not lost because [...]

Unfortunately I cannot find it clearly explained in
that way. To be honest, I cannot even find the first
statement clearly explained.

What I mean is: by using Kruskal-Szekeres coordinates
we can follow any molecule, or larger object, that
enters the black hole, and there is no clear indication
that it ever loses information at all! There might be
tidal forces tearing it apart, but that need not in
general destroy information and also that need not
happen at the event horizon (in fact the Schwarzschild
radius has no special local properties at all, as the
K-S coordinates prove). Finally, singularities may be
present somewhere inside, but we don't know the physics
there, so we cannot claim anything about what happens
to information at those sites.

Actually, for statement 2) I also never found a really
satisfying explanation, but let's leave that out, since
without *two conflicting statements* there is no
paradox anyway.

So why do people feel there is a paradox?!


A very good introductory article is in the magazine Aeon

https://aeon.co/essays/is-the-black-...antum-computer
  #9  
Old April 10th 16, 04:47 PM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Paradox unexplained

Op vrijdag 8 april 2016 23:21:25 UTC+2 schreef jacobnavia:
Le 01/04/2016 16:47, Jos Bergervoet a écrit :

So why do people feel there is a paradox?!


A very good introductory article is in the magazine Aeon

https://aeon.co/essays/is-the-black-...tre-a-quantum=

-computer

Sorry but I have troubles with this article.

It starts with the text:

"But according to the laws of quantum mechanics, all of the information
about your body's build and function will prevail.

The relations between the atoms, the uncountable particulars that made
you you, will remain forever preserved, albeit in unrecognisably
scrambled form - lost in practice, but immortal in principle."
This seams like a simple text but it is very difficult to prove
that it is true. What means "body's build and function"?

If this is not clear then the whole text is not clear and indirect
its "deeper" meaning.

Next we read:

"according to our current physical understanding, information cannot
survive an encounter with a black hole."

The problem is what has the concept of "information" to do with
the physical evolution of a BH?

Next we read:

"the information paradox makes it aptly clear that physicists still do
not understand the fundamental laws of nature."

No it does not.

The problem is we do not know the details of the physical processes
involved in the lifecycle process of BH's.

And IMO this has nothing to do with the information paradox
which is also not clear.

When you study QM, for example
https://en.wikipedia.org/wiki/Densit...d_mixed_states
you can see what this means related to (polarized) light.
This seems rather simple.

The problem is how can you use that in the context of the above
stated problem: "body's build and function".
How can you use that in relation to the lifecycle of a star who
becomes a red giant or supernova. I think that is tricky.

Nicolaas Vroom

  #10  
Old April 10th 16, 05:05 PM posted to sci.astro.research
Phillip Helbig
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Posts: 38
Default Paradox unexplained

In article ,
Nicolaas Vroom writes:

"But according to the laws of quantum mechanics, all of the information
about your body's build and function will prevail.

The relations between the atoms, the uncountable particulars that made
you you, will remain forever preserved, albeit in unrecognisably
scrambled form - lost in practice, but immortal in principle."
This seams like a simple text but it is very difficult to prove
that it is true.


One doesn't prove it directly, but proves the underlying assumptions,
from which it follows.

What means "body's build and function"?


Essentially all information about the body.

"according to our current physical understanding, information cannot
survive an encounter with a black hole."

The problem is what has the concept of "information" to do with
the physical evolution of a BH?


A lot. Again, and this has already been pointed out here, according to
GR a black hole is COMPLETELY characterized by mass, angular momentum,
and charge, so there is no record left of what went into it.

"the information paradox makes it aptly clear that physicists still do
not understand the fundamental laws of nature."

No it does not.


Yes it does.

The problem is we do not know the details of the physical processes
involved in the lifecycle process of BH's.


Unless you have some alternative theory which shows that information is
NOT lost, then the processes are irrelevant.

And IMO this has nothing to do with the information paradox
which is also not clear.


It's not a matter of opinion; it's a matter of using the terms like
everyone else uses them.

 




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